This invention relates to a method and apparatus for covering the face of a blank of mineral or organic glass having a plane or curved profile, such as a blank of lens glass, with a protective plastic film.
When the concave surfaces of glass blanks are covered with a protective plastic film, it is current practice to resort to a process of at least two stages. During the first stage of the process, the goal is preliminary adherence of the film with minimum entrapment of air between the glass surface and the film. In the final stage of the process, higher temperature and pressure are applied to complete the bonding of the film to the glass surface. The final stage of the process is generally conducted in an autoclave. The resulting product is a covered blank that is completely transparent.
When the blank is covered by this process, the final result is often unsatisfactory. One cause is an imperfect initial contact during the first stage of the process.